The present invention relates to a physical quantity sensor apparatus and, in particular, relates to a physical quantity sensor apparatus which outputs detected information in a form of an optical signal and is applicable for use as an air flow sensor used in an automobile engine control system.
In a conventional automobile engine control system disclosed in JP-A-63-179217(1988), the signal transmission between sensors at a variety of locations, and a control unit is generally performed by voltage signals via electrical signaling lines. Therefore, their sensors such as those disclosed in JP-A-62-153711(1987) are constructed to output the detected information in the form of an electrical signal.
On one hand, presently, the number of detected information in an automobile has been increasing and the type of detected information has been diversifying. A light-weight automobile is highly desired in order to improve fuel consumption. To provide such requirements, the development of the LAN system in an automobile has been advanced wherein a wireharness which is a bundle of wires is eliminated, and information is transmitted via an optical fiber cable.
The developement of LAN system in an automobile wherein the optical fiber cable is used as the signal transmission means has obtained a certain agreeable level as an optical communication system for an automobile. However, as will be apparent from the above mentioned prior document, the variety of conventional sensors used for an automobile are still constructed so as to output the detected information in a form of electrical signal such that a satisfactory interface between the output portions of the sensors and the other portions of the LAN system in an automobile is not obtained. Further, as a LAN system is built in an automobile by making use of sensors which output electrical signals, electro-optical converters hare required between the optical fiber cable constituting the signal transmission means and the variety of sensors thereby the structure thereof is complex and a troublesome assembly thereof results.